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→Biological classification of elements
===Biological classification of elements===
===Biological classification of elements===
[[File:UNN_Medical_Geology_Fig_3.png|thumb|400px|{{figure number|3}}Periodic table illustrating major elements (pink), minor elements (blue), trace elements (yellow), and noble gases (gray) in the biosphere. Those in green are essential trace elements. Known established toxic elements are shown in red (Selinus et al, 2013).]]
Good understanding of health issues arising from geologic materials comes from sound knowledge of the classification of elements from the biological point of view because not all elements have been proven to cause health problems. Therefore, medical geology is mainly geared towards identifying and understanding the harmful elements (Selinus et al, 2013).
Good understanding of health issues arising from geologic materials comes from sound knowledge of the classification of elements from the biological point of view because not all elements have been proven to cause health problems. Therefore, medical geology is mainly geared towards identifying and understanding the harmful elements (Selinus et al, 2013).
Naturally occurring elements are classified into major elements, minor elements, trace elements and noble gases (Fig. 3).
Naturally occurring elements are classified into major elements, minor elements, trace elements and noble gases ([[:File:UNN_Medical_Geology_Fig_3.png|Figure 3]]).
[[File:UNN_Medical_Geology_Fig_3.png|thumb|400px|{{figure number|3}}]]
According to Nordberg, and Cherian (2005) major elements are those elements that are needed in large quantities in the body; each makes more than 1% of the human body (oxygen alone making up to 65% of the body). They include hydrogen, oxygen, carbon and nitrogen. These elements form most of the DNA structures in the human body; they occur in most organs and tissues. In addition, they are the main building blocks of enzymes; they are also important constituents of the cell membrane, inter-cellular, intracellular fluids and are actively involved in metabolic processes, all in their ionic states. Hence, in the event of high intake of these elements, the body has many ‘sites’ where they can be used. Nature provides a good abundance of these elements as it has been observed that the concentration of these elements is fairly the same in similar rocks and show the least variance compared to the minor and trace elements. Thus, they rarely pose problems (Selinus et al, 2013).
According to Nordberg, and Cherian (2005) major elements are those elements that are needed in large quantities in the body; each makes more than 1% of the human body (oxygen alone making up to 65% of the body). They include hydrogen, oxygen, carbon and nitrogen. These elements form most of the DNA structures in the human body; they occur in most organs and tissues. In addition, they are the main building blocks of enzymes; they are also important constituents of the cell membrane, inter-cellular, intracellular fluids and are actively involved in metabolic processes, all in their ionic states. Hence, in the event of high intake of these elements, the body has many ‘sites’ where they can be used. Nature provides a good abundance of these elements as it has been observed that the concentration of these elements is fairly the same in similar rocks and show the least variance compared to the minor and trace elements. Thus, they rarely pose problems (Selinus et al, 2013).